Mullite-aluminum titanate body and method for making same

ABSTRACT

This invention relates to a mullite-aluminum titanate body having a low coefficient of thermal expansion of less than 15×10 −7  C −1 , a high porosity of at least 38% by volume, a median pore diameter of at least 8 microns, and a narrow pore size distribution as characterized by the relation (d 50 -d 10 )/d 50  being less than 0.50 corresponding to a high degree of interconnected porosity. The inventive ceramic body also contains at least 0.10% by weight metal oxide, the metal being either yttrium, calcium, bismuth, a lanthanide metal or combinations of thereof. The inventive ceramic body is particularly useful as a wall-flow filter for diesel exhaust. A method of fabrication is provided where the sintering temperature is between 1375°-1550° C.

BACKGROUND OF THE INVENTION

The present invention relates to a mullite-aluminum titanate ceramic body that has improved properties for use in high temperature applications and a method for making the same.

Porous refractory ceramics have long been used as particulate filters in hot gas or corrosive environments such as advanced coal-based gas turbine cycles, municipal and industrial waste incinerators, and diesel or natural-gas engine exhaust systems. For such applications, ceramic particulate filters must possess chemical inertness, thermal shock resistance, high filtration efficiency, low pressure drop, and adequate strength. In particular, a diesel particulate filter (DPF) ideally combines low CTE (for thermal shock resistance), low pressure drop (for engine efficiency), high filtration efficiency (for removal of most particles from the exhaust stream), high strength (to survive handling, canning, and vibration in use), and low cost.

Candidate materials for DPFs include cordierite, silicon carbide and aluminum titanate based ceramics. Cordierite is attractive due to its low cost, low CTE, and good strength. However, the relatively low volumetric heat capacity (approximately 2.8 J cm⁻³ ° C.-⁻¹ at 800K) and low thermal conductivity of cordierite can result in unacceptably high temperatures during operation when the filters are regenerated under certain conditions. Further, obtaining a well-interconnected pore microstructure in cordierite filters, in combination with low porosity required for high thermal mass, has been a challenge.

Silicon carbide filters have an advantage of a well-interconnected porosity for low pressure drop. Higher volumetric heat capacity (approximately 3.6 J cm⁻³ ° C.⁻¹ at 800K) and high thermal conductivity, coupled with a very high melting point, make silicon carbide thermally durable. However, silicon carbide is relatively expensive. Furthermore, the high coefficient of thermal expansion requires silicon carbide filters to be fabricated as cement-bonded segments, adding to manufacturing cost and raising concerns about their long-term thermo-mechanical durability.

Aluminum titanate based ceramics and specifically mullite-aluminum titanate (MAT) ceramics offer a very high volumetric heat capacity (approximately 3.9 to 4.0 J cm⁻³ ° C.⁻¹ for fully dense MAT at 800K) in combination with a low CTE. Further, MAT ceramics have excellent chemical durability and high melting point.

However, in the manufacture of MAT bodies sintering temperatures greater than 1600° C. are often required to achieve sufficient grain growth for microcracking and low thermal expansion. Such high heating temperatures add cost to manufacturing and final product. To reduce the sintering temperature some approaches have utilized the addition of chemical components. Nonetheless, such methods often result in a strong sensitivity of the physical properties, including CTE, porosity, or pore size, to the firing temperature, which is undesirable for manufacturability. Also, desired properties for DPF use are not expected to be achieved. Further, many methods for making aluminum titanate-based bodies require the use of pre-reacted aluminum titanate and/or mullite powders, which also increase the manufacturing cost.

A need therefore exists to have a mullite-aluminum titanate body that can be manufactured at lower sintering temperatures with properties that are useful for high temperature filtration applications.

SUMMARY OF THE INVENTION

MAT ceramic bodies of the present invention offer low thermal expansion, high thermal shock resistance, a narrow pore size distribution and greater interconnectivity of the porosity, and are fabricated at lower sintering temperatures of between 1375° C.-1550° C. by using a metal oxide sintering additive in the raw material batch. The metal oxide is added in an amount of at least 0.10% by weight, in some applications between 0.10%-5.0% by weight, the oxide relating to a metal selected from the group consisting of yttrium, bismuth, calcium, lanthanide metals, and combinations thereof.

In one embodiment the inventive materials exhibit a coefficient of thermal expansion (RT-1000° C.) less than 15×10⁻⁷ C⁻¹, a porosity of at least 38% by volume, a median pore diameter of at least 8 micrometers, and a narrow pore size distribution as characterized by the relation (d₅₀-d₁₀)/d₅₀ being not more than 0.50 which corresponds to a high degree of interconnected porosity.

The inventive bodies are especially useful in high temperature applications including wall-flow filters for diesel exhaust filtration. In one such embodiment the filter is a plugged, honeycomb body composed of the inventive MAT ceramic and exhibiting a coefficient of thermal expansion or CET (RT-1000° C.) of not greater than 10×10⁻⁷ C⁻¹, a porosity of between 45-60% by volume, a median pore diameter of between 10-20 micrometers, and a narrow pore size distribution as characterized by the relation (d₅₀-d₁₀)/d₅₀ being not greater than 0.35 which corresponds to a high degree of interconnected porosity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a scanning electron micrograph of the as-fired surface of Inventive Example 16, showing the unique domain-type microstructure of radiating crystals;

FIG. 2 is a scanning electron micrograph of the as-fired surface of Comparative Example C5, showing the absence of any groups of radiating crystals;

FIG. 3 shows the changes in %porosity, median pore diameter, and mean CTE (RT-1000° C.) as a function of the amount of Y₂O₃ added to the raw material mixture when fired at 1400° C.;

FIG. 4 shows the changes in %porosity, median pore diameter, and mean CTE (RT-1000° C.) as a function of the amount of Y₂O₃ added to the raw material mixture when fired at 1500° C.;

FIG. 5 is a scanning electron micrograph of a polished cross section of Inventive Example 60 showing the high degree of interconnected porosity of the inventive material;

FIG. 6 shows the relationship between the pressure drop versus soot loading behavior of a commercially-available cordierite DPF, a silicon carbide DPF, and a DPF comprising the ceramic of Inventive Example 72, each having approximately the same heat capacity per unit volume; and,

FIG. 7 shows the values for % porosity, median pore diameter (microns) and CTE (RT-1000° C., 10⁻⁷ ° C.⁻¹) for Examples 89 to 93 plotted versus the temperature at which the examples were fired.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The ceramic body of the present invention is composed primarily of mullite and aluminum titanate phases, while also including at least 0.10% by weight of one or more metal oxides in which the metal is selected from the group consisting of bismuth, calcium, yttrium, lanthanides and combinations thereof. For certain applications the metal oxide is limited to an amount of between 0.10% to 5.0% by weight.

It has been observed that the addition of one or more of the recited metal oxides lowers the coefficient of thermal expansion and increases the median pore diameter without substantially reducing the amount of porosity in the fired body. A low CTE is desired for high thermal shock resistance, while a large median pore diameter contributes to low pressure drop.

Furthermore, the metal oxide sintering additives enable the use of lower sintering temperatures. Also, the physical properties of the inventive bodies are not sensitive to the firing temperature employed such that conventional kilns without the need for sophisticated and expensive temperature controls can be used. Further, as a result of the metal oxide sintering additives used the physical properties are not sensitive such that the inventive MAT bodies can be used at temperatures higher than the sintering temperatures used, for a period of duration of 5-10 hours or somewhat more.

In fabricating the inventive ceramic bodies a raw material mixture is first provided. The inorganic powders are selected from sources of: (a) alumina such as corundum, gamma-alumina or another transitional alumina, boehmite, alumina hydroxide (gibbsite) and mixtures thereof, (b) aluminosilicate such as mullite, kyanite, sillimanite, kaolin, calcined kaolin, pyrophyllite and mixtures thereof, (c) silica such as quartz, cristobalite, zeolite, diatomaceous earth, a silicon organometallic compound, fused silica, colloidal silica, other amorphous silica, and combinations thereof, and (d) titanium dioxide such as rutile, anatase, amorphous titania, and mixtures thereof. Optionally, pre-reacted aluminum titanate may be used as a raw material, but is not required nor desired.

It is important that in the raw material mixture of powders the weighted average of the median particle or agglomerate diameters of the constituent inorganic powders, denoted D₅₀, is at least 6 microns. The value of D₅₀ is calculated as D₅₀=Σ[(w_(i))(d_(50,i))]/Σ(w_(i)) in which w_(i) denotes the weight percentage of each inorganic powder exclusive of the metal oxide sintering additive, and d_(50,i) is the median particle or agglomerate diameter of that same inorganic powder. The particle or agglomerate diameters are measured by a laser diffraction technique. A weighted average particle size of less than 6 microns would result in a pore size finer than 8 microns in the final MAT ceramic, contrary to the required properties of the present invention.

The alumina source has a median particle size greater than 15 microns. When the particle size of the titania source is greater than 5 microns the porosity of the body is desirably increased without the need for large amounts of a pore-forming agent. Preferably, both the alumina source and titanium dioxide source have median particle or agglomerate diameters of at least 10 microns.

The raw material mixture further includes a metal oxide sintering additive. Suitable metal oxides for purposes of the present invention include but are not limited to bismuth oxide, calcium carbonate, calcium hydroxide, calcium aluminate, calcium titanate, calcium silicate, yttrium or rare earth oxide, hydroxide, carbonate, fluoride-carbonate, aluminate, silicate, titanate, chloride, nitrate, acetate, or other soluble or insoluble salt, or a mixed rare earth concentrate such as bastnasite, calcined bastnasite, or monazite. The metal oxide sintering additive preferably has a median particle size of less than 5 microns, or is in a water-soluble state. The metal oxide additive is present in an amount of at least 0.10% by weight, or preferably between 0.10% to 5.0% by weight super-addition to the other inorganic raw materials that react to form aluminum titanate and mullite phases. By super-addition is meant that to 100 grams of inorganic raw material mixture are added for example between 0.10 to 5 grams of metal oxide.

Optionally, at least 0.05% by weight molybdenum oxide or tungsten oxide may be added to the raw material mixture. The addition of a molybdenum oxide or tungsten oxide source to the raw material mixture increases the amount of porosity in the fired ceramic, thus requiring less pore forming agent in the raw material mixture.

Optionally, a pore former may be added to tailor the porosity of the final ceramic body. The raw material mixture may include up to 20× grams per 100 grams of the inorganic raw materials, where X is the density of the pore former particle in grams per cubic centimeter. The pore forming agent may be any particulate material that undergoes combustion or vaporization during heating of the green body so as to leave behind pores after the sample has been fired.

Examples of pore forming agents include, but are not restricted to, graphite, amorphous carbon, cellulose, wood flour, nut shell flour, starches, and synthetic polymers such as polyethylene, polystyrene, and polyacrylate. The pore forming agent preferably has a median particle or agglomerate diameter of between 10-100 microns. Finer particle sizes result in an undesirably finer pore size and higher pressure drop when the body is used as a filtration device. Coarser particle sizes yield large pores than weaken the body and may result in reduced filtration efficiency if the body is used as a filter.

The raw materials and pore formers are further mixed with organic and/or organometallic binders, lubricants, and plasticizers and aqueous or non-aqueous solvents to form a plastic mixture that can be shaped by any conventional means such as by molding or extrusion through a die, such as for example to form a honeycomb structure. The green-formed body is then dried and fired in air to a temperature of between 1375° to 1550° C. and held for approximately 1 to 15 hours before cooling to room temperature.

MAT ceramics according to the present invention exhibit a low coefficient of thermal expansion (CTE) from a microcracked structure, good thermal durability, good strength, and highly interconnected porosity. The amount of mullite in the body is estimated to be between 2-60% by weight, and preferably between 15-40% by weight.

In one embodiment the inventive ceramic body is characterized by the following properties: a coefficient of thermal expansion (RT-1000° C.) less than 15×10⁻⁷ C⁻¹, a porosity of at least 38% by volume, a median pore diameter of at least 8 micrometers, and a narrow pore size distribution as characterized by the relation (d₅₀-d₁₀)/d₅₀ being not more than 0.50 which corresponds to a high degree of interconnected porosity. The values d₁₀ and d₅₀ are defined as the pore diameters at 10% and 50% of the cumulative pore size distribution based upon volume, as measured by mercury porosimetry, with d₁₀<d₅₀. Thus, d₅₀ is the median pore diameter, and d10 is the pore diameter at which 10% of the pores are finer, based upon volume.

A narrow pore size distribution corresponds to a greater interconnectivity of the porosity, which results in a lower pressure drop under soot-loaded conditions when the body is used as a diesel particulate filter. The material strength of the MAT ceramic, as indicated by the modulus of rupture (MOR) using the four point method on a cylindrical rod, is at least 500 psi.

In another embodiment the inventive MAT ceramic is used in the fabrication of filters for diesel exhaust and in particular as a wall-flow filter. A wall-flow filter comprises a plugged, honeycomb body having a plurality of parallel end-plugged cell channels traversing the body from a frontal inlet end to an outlet end thereof. Such structures are well known in the art. Part of the total number of cells at the inlet end are plugged along a portion of their lengths, and the remaining part of cells that are open at the inlet end are plugged at the outlet end along a portion of their lengths. This plugging configuration allows for engine exhaust passing through the cells of the honeycomb from the inlet end to the outlet end to flow into the open cells, through the cell walls, and out of the structure through the open cells at the outlet end. Suitable cellular densities for diesel particulate filters range from 70 cells/in² (10.9 cells/cm²) to 400 cells/in² (62 cells/cm²).

In another embodiment a DPF comprising the inventive material is preferably characterized by the following properties: a coefficient of thermal expansion (RT-1000° C.) not greater than 10×10⁻⁷ C⁻¹, a porosity of between 45-60% by volume, a median pore diameter of between 10-20 micrometers, and a narrow pore size distribution as characterized by the relation (d₅₀-d₁₀)/d₅₀ being not greater than 0.35 which corresponds to a high degree of interconnected porosity.

EXAMPLES

The invention is further illustrated with the following non-limiting examples. Inventive and comparative samples are prepared by admixing the inorganic raw materials, metal oxide additives, and pore-forming agents with 4 to 6 wt % methyl cellulose binder, 0.15 wt % triethanol amine, 1% tall oil, and 14 to 18 wt % water. The mixture is plasticized in a stainless steel muller and extruded as 5/16-inch diameter rod and 1-inch, 2-inch, or 5.7-inch diameter honeycomb. Parts are dried and then fired in a gas or electric kiln at 1400° to 1500° C. and held for 4 to 10 hours.

After firing, the porosities of the samples are characterized by mercury porosimetry, the CTEs measured by dilatometry, and the modulus of rupture (MOR) by the four-point method on 5/16-in diameter rods. MOR values are reported in pounds per square inch (psi). Some samples are also crushed and their crystalline phases identified by powder x-ray diffractometry. Pore diameters (d₁₀, d₅₀ and d₉₀) are in micrometers. The meanings of d₁₀ and d₅₀ has been defined previously. The value of d₉₀ is the pore diameter for which 90% of the pores, by volume, are finer in diameter thus d₁₀<d₅₀<d₉₀. Coefficients of thermal expansion are in units of 10⁻⁷° C.⁻¹.

Selected 2-inch and 5.7-inch diameter parts, 6-inches long, are prepared as filters by plugging the ends of alternate channels on one face, and then plugging the ends of the adjacent channels on the opposite face, using a cold-set cement. Pressure drops across the length of the filters are measured at ambient temperature at air flow rates of 26.25 standard cubic feet per minute (scfm) on 2-inch diameter filters, and 210 scfm on the 5.7-inch diameter filters. The filters are then progressively loaded with artificial high surface area carbon soot at loadings from about 0.5 grams/liter to about 4.5 grams/liter, and the pressure drops measured at the same flow rate for each soot loading. Pressure drop values reported at 5 g/l soot loading are calculated by linear extrapolation of the data at lower soot loadings.

Median particle sizes of the raw materials used in the present inventive and comparative examples are listed in Table 1. Raw materials and properties of the examples are provided in Tables 2 to 23. Nominal percentages of aluminum titanate (Al₂TiO₅) and mullite (3Al₂O₃-2SiO₂) for each composition are by weight. All raw materials are also in parts by weight.

Examples prefixed by the letter “C” denote comparative (non-inventive) examples. Amounts of phases measured by powder XRD are denoted as major (M), minor (m), very minor (vm), trace (tr), small or very small trace (s.tr. and v.s.tr), or absent (0). Examples in Tables 2 to 19, and 23, were fired in electric furnaces; those in Tables 20-22 utilized either gas or electric furnaces, as indicated in the tables. In Tables 2-23, “MPS” denotes median particle size (diameter) in micrometers. MPS of the inorganic raw materials is equivalent to D₅₀ and is also in micrometers. In the examples of Tables 2 to 23, the MPS of all inorganic raw materials includes contributions from alumina, aluminum hydroxide, titania, kaolin, and quartz.

Examples C1 and C2 in Table 2 show that, in the absence of a metal oxide addition selected from the inventive group of compounds, ceramic bodies of aluminum titanate+mullite fired at 1400 or 1500° C. have a CTE greater than 15. Comparative examples C3 and C4 show that, although the addition of 2.78% Y₂O₃ reduces the CTE to less than 15, the median pore size is undesirably less than 8 microns when the weighted average of the median particle sizes of the inorganic raw materials is less than 6 microns.

Table 3 shows that, even when the weighted average of the median particle sizes of the inorganic raw materials is greater than 6 microns, the CTEs of the aluminum titanate +mullite ceramics are greater than 15 and the median pore sizes are less than 8 microns in the absence of a metal oxide addition selected from the inventive group of compounds, regardless of whether the compositions are fired at 1400° C. or at 1500° C. Furthermore, in the absence of the inventive sintering additive, substantial amounts of unreacted alumina and titania are present when fired at 1400° C. for these coarse raw materials.

By contrast, the inventive examples in Table 4 demonstrate that, when the weighted average of the median particle sizes of the inorganic raw materials is greater than 6 microns and the raw materials mixture contains Y₂O₃, the CTEs of the aluminum titanate +mullite ceramics are less than 7 and the median pore sizes are greater than 8 microns when at least 1.0 wt % Y₂O₃ is added to this raw material mixture.

Examples 2 and 3 further show that the %porosity of the ceramic bodies is desirably increased by the addition of at least 1.0 wt % MoO₃ to the raw materials. FIG. 1 illustrates that the microstructure of Inventive Example 16 consists of “domains” of radiating aluminum titanate crystals. Such domains provide a unique microstructure that may influence the nature of the microcracking in the inventive ceramics. This microstructure is contrasted with that of Comparative Example C5 in FIG. 2, which depicts the lack of domains when an inventive metal oxide additive is absent.

The examples in Table 5 illustrate that firing the inventive compositions at 1500° C. still yields very low CTE and a median pore size greater than 8 microns while still preserving desirable high porosities. Thus, the inventive sintering additives do not result in excessive densification of the ceramic bodies with increasing temperature, and are therefore conducive to manufacturing processes that do not require stringent and expensive control of the firing temperature to within a very narrow range.

Tables 6 and 7 provide additional inventive examples based upon Y₂O₃ with or without MoO₃ for 80% aluminum titanate/20% mullite and 70% aluminum titanate/30% mullite compositions using various raw material combinations, some including kaolin as a source of silica and alumina, sintered at only 1400° C. Tables 8 and 9 show that inventive properties are still retained when these compositions are fired at 1500° C.

Tables 10 and 11 characterize the dependence of the physical properties of the MAT ceramics on the amount of Y₂O₃ addition to the raw material mixture, and the results are shown in FIGS. 3 and 4. Table 10 illustrates that when an 80% aluminum titanate/20% mullite composition in which the weighted average of the median particle sizes of the inorganic raw materials is 9.3 microns is fired at 1400° C., more than 0.5% Y₂O₃ is required to maintain a median pore size of at least 8 microns and a CTE less than 15. Table 11 shows that when these compositions are fired at 1500° C., the amount of Y₂O₃ must be less than 5% to maintain at least 38% porosity and greater than 0.1% to maintain a median pore size greater than 8 microns. It will be appreciated that even lower amounts of Y₂O₃ could be utilized at 1500° C. if the weighted average of the median particle sizes of the raw materials was greater than 9.3 microns. FIGS. 3 and 4 show that an amount of Y₂O₃ between 1 and 3% is especially preferred for this raw material combination because the porosity, pore size, and CTE are relatively stable within this range of metal oxide addition.

The examples in Tables 12 and 13 show that, in addition to yttrium oxide, the oxides of the lanthanides metals, and their combinations, are effective in obtaining inventive bodies with useful CTE, porosity, and pore size. Examples 48 and 57 demonstrate that the lanthanide oxides may be provided in the form of a calcined ore comprised primarily of the oxides of lanthanum, cerium, praseodymium, and dysprosium.

Tables 14 and 15 illustrate that a source of calcium oxide, in this case calcium carbonate, is also effective as a sintering additive to promote low CTE and coarse pore size without reducing porosity. However, sources of the oxides of strontium, indium, and tin do not constitute inventive additives because they either result in high CTE or low strength.

Tables 16 and 17 demonstrate that the oxides of molybdenum, boron, niobium, tungsten, zinc, and zirconium alone are not effective sintering additives. However, bismuth oxide does serve as a useful sintering additive, provided that the firing temperature is greater than 1400° C., and the raw materials have a median pore size greater than 6 microns.

In example C29, the median pore size is smaller than 8 microns because D₅₀ of the inorganic raw materials is less than 6 microns. However, it will be appreciated that the median pore size the MAT ceramic prepared with bismuth oxide addition can be increased to greater than 8 microns by the use of coarser raw materials while still preserving a CTE (RT-1000° C.) below 15×10⁻⁷° C.⁻¹ and a porosity greater than 38%.

Table 18 shows that, by increasing the median particle size of the alumina sources, the median pore size can be increased and a narrow pore size distribution maintained even when the particle size of the titania source remains very small. FIG. 5 depicts the well interconnected porosity of Inventive Example 66.

The examples in Table 19 illustrate that the particle size of both the titania and alumina sources can be varied while maintaining the inventive properties. Coarse titania is especially useful for increasing the porosity of the fired body without the need for larger amounts of additional pore forming agent.

Example 72 also shows that a filter prepared from the inventive body exhibits a very low clean and soot-loaded pressure drop as a diesel particulate filter. The full pressure drop versus soot loading curve measured at room temperature and a flow rate of 210 standard cubic feet per minute is depicted in FIG. 6 and compared with the pressure drop curves for cordierite and silicon carbide filters of the same size and approximately the same volumetric heat capacity measured under the same test conditions.

The three filters are all approximately 5.66 inches diameter and 6 inches in length, and pressure drops were all measured at room temperature and a flow rate of 210 standard cubic feet per minute. The cordierite example has a cell density of 190 cells/inch² and 0.017 inch walls. The silicon carbide example has a cell density of 320 cells/inch2 and 0.010 inch walls. The inventive example has a cell density of 311 cells/inch² and 0.011 inch walls. The figure demonstrates the excellent low pressure drop exhibited by filters of the inventive material.

The examples of Tables 20 to 22 demonstrate that the CTE, porosity, and median pore size of the inventive materials do not change greatly for firing temperatures from 1415 to 1475° C., and that the inventive properties are obtained whether the body is fired in an electric kiln or a gas kiln. The properties for Inventive Examples 89-93 are plotted against the firing temperature in FIG. 7.

Table 23 shows the changes in length, CTE, and MOR of an inventive body after cycling 300 times between 200 and 1100° C. in air. The small differences after thermal cycling demonstrate the excellent dimensional and physical stability of the inventive examples.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of the disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims. TABLE 1 Median Particle Diameter Raw Material (microns) Alumina A 6.8 Alumina B 9.0 Alumina C 9.0 Alumina D 23.8 Alumina E 41.8 Aluminum hydroxide A 11.5 Aluminum hydroxide B 13.2 Aluminum hydroxide C 21.0 Titania A 0.50 Titania B 13.7 Titania C 22.7 Kaolin A 9.9 Quartz A 3.7 Quartz B 23.4 Quartz C 25.4 Graphite A 35.0 Graphite B 49.0

TABLE 2 Example Number C1 C2 C3 C4 % Al₂TiO₅ 80 80 80 80 % Mullite 20 20 20 20 Weight Percent Y₂O₃ — — 2.78 2.78 Alumina A 53.52 53.52 53.52 53.52 Titania A 34.56 34.56 34.56 34.56 Kaolin A 11.92 11.92 11.92 11.92 Graphite A 25.00 25.00 25.00 25.00 MPS Alumina sources 6.8 6.8 6.8 6.8 MPS Titania source 0.50 0.50 0.50 0.50 MPS Quartz — — — — MPS Inorganic Raw Materials 5.0 5.0 5.0 5.0 Firing and Properties Firing Temperature (° C.) 1400 1500 1400 1500 Hold Time (hours) 4 4 4 4 CTE (RT-1000° C.) 44.8 28.1 12.3 5.7 % Porosity 48.8 51.4 47.9 38.9 d₅₀ 3.9 3.8 5.8 7.4 d₁₀ — — — — d₉₀ — — — — (d₅₀-d₁₀)/d₅₀ — — — — (d₉₀-d₁₀)/d₅₀ — — — — MOR rod (psi) 2335 1490 1141 1073 Al₂TiO₅ M M M M Mullite m m m m Al₂O₃ m 0 tr tr TiO₂ m 0 0 0

TABLE 3 Example Number C5 C6 C7 C8 C9 C10 % Al₂TiO₅ 80 90 95 80 90 95 % Mullite 20 10 5 20 10 5 Weight Percent MoO₃ — — — — — — Y₂O₃ — — — — — — Alumina C 41.48 39.94 39.18 41.48 39.94 39.18 Aluminum 20.00 20.00 20.00 20.00 20.00 20.00 hydroxide B Titania A 33.27 37.43 39.51 33.27 37.43 39.51 Quartz A 5.25 2.62 1.31 5.25 2.62 1.31 Graphite A 25.00 25.00 25.00 25.00 25.00 25.00 MPS Alumina 10.4 10.4 10.4 10.4 10.4 10.4 sources MPS Titania 0.50 0.50 0.50 0.50 0.50 0.50 source MPS Quartz 3.7 3.7 3.7 3.7 3.7 3.7 MPS Inorganic 6.7 6.5 6.4 6.7 6.5 6.4 Raw Materials Firing and Properties Firing 1400 1400 1400 1500 1500 1500 Temperature (° C.) Hold Time 4 4 4 4 4 4 (hours) CTE 50.1 44.3 36.8 33.5 28.2 22.7 (RT-1000° C.) % Porosity 49.8 50.4 49.9 52.6 55.4 54.6 d₅₀ 4.4 4.4 4.6 6.7 6.2 6.3 d₁₀ 2.2 2.1 2.1 3.4 3.1 3.2 d₉₀ 9.0 8.7 8.4 14.5 20.6 13.2 (d₅₀ − d₁₀)/d₅₀ 0.50 0.51 0.53 0.50 0.51 0.50 (d₉₀ − d₁₀)/d₅₀ 1.55 1.50 1.36 1.66 2.83 1.60 MOR rod (psi) 2084 1264 1145 2209 1623 1523 Al₂TiO₅ M M M M M M Mullite m tr 0 m tr 0 Al₂O₃ M M M tr m m TiO₂ M M M tr m m

TABLE 4 Example Number 1 2 3 4 5 % Al₂TiO₅ 80 80 80 90 95 % Mullite 20 20 20 10 5 Weight Percent MoO₃ — 2.61 1.30 — — Y₂O₃ 2.78 1.39 2.78 2.73 1.35 Alumina C 41.48 41.48 41.48 39.94 39.18 Aluminum hydroxide B 20.00 20.00 20.00 20.00 20.00 Titania A 33.27 33.27 33.27 37.43 39.51 Quartz A 5.25 5.25 5.25 2.62 1.31 Graphite A 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 10.4 10.4 10.4 10.4 10.4 MPS Titania source 0.50 0.50 0.50 0.50 0.50 MPS Quartz 3.7 3.7 3.7 3.7 3.7 MPS Inorganic Raw 6.7 6.7 6.7 6.5 6.4 Materials Firing and Properties Firing Temperature 1400 1400 1400 1400 1400 (° C.) Hold Time (hours) 4 4 4 4 4 CTE (RT-1000° C.) 6.8 4.1 3.2 −0.8 −5.1 % Porosity 51.8 53.7 54.5 45.9 46.4 d₅₀ 9.2 8.5 9.7 8.5 8.3 d₁₀ 5.8 5.3 6.4 6.1 5.7 d₉₀ 17.6 17.9 20.4 30.2 15.1 (d₅₀ − d₁₀)/d₅₀ 0.37 0.37 0.34 0.28 0.31 (d₉₀ − d₁₀)/d₅₀ 1.28 1.48 1.44 2.83 1.13 MOR rod (psi) 602 793 586 946 897 Al₂TiO₅ M M M M M Mullite m m m 0 0 Al₂O₃ tr tr vm tr m TiO₂ vm tr vm tr tr

TABLE 5 Example Number 6 7 8 9 10 11 12 % Al₂TiO₅ 80 80 80 80 90 90 95 % Mullite 20 20 20 20 10 10 5 Weight Percent MoO₃ 2.61 2.61 1.30 — — — — Y₂O₃ 1.39 2.78 2.78 2.78 1.36 2.73 1.35 Alumina C 41.48 41.48 41.48 41.48 39.94 39.94 39.18 Aluminum hydroxide B 20.00 20.00 20.00 20.00 20.00 20.00 20.00 Titania A 33.27 33.27 33.27 33.27 37.43 37.43 39.51 Quartz A 5.25 5.25 5.25 5.25 2.62 2.62 1.31 Graphite A 25.00 25.00 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 10.4 10.4 10.4 10.4 10.4 10.4 10.4 MPS Titania source 0.50 0.50 0.50 0.50 0.50 0.50 0.50 MPS Quartz 3.7 3.7 3.7 3.7 3.7 3.7 3.7 MPS All Inorganic Raw Materials 6.7 6.7 6.7 6.7 6.5 6.5 6.4 Firing and Properties Firing Temperature (° C.) 1500 1500 1500 1500 1500 1500 1500 Hold Time (hours) 4 4 4 4 4 4 4 CTE (RT-1000° C.) −3.6 −5.9 −2.8 0.8 −4.9 −7.6 −12.5 % Porosity 52.5 50.9 51.8 48.2 47.7 44.9 44.4 d₅₀ 9.8 10.8 11.5 10.4 9.9 10.6 10.5 d₁₀ 6.8 8.3 8.8 8.3 7.0 8.4 8.1 d₉₀ 14.9 15.4 56.4 16.5 17.8 44.0 17.7 (d₅₀ − d₁₀)/d₅₀ 0.31 0.23 0.23 0.20 0.29 0.21 0.23 (d₉₀ − d₁₀)/d₅₀ 0.83 0.65 4.14 0.78 1.09 3.36 0.91 MOR rod (psi) 1040 1018 842 736 1063 1195 954 Al₂TiO₅ M M M M M M M Mullite m m m m tr tr 0 Al₂O₃ m m m tr tr m tr TiO₂ 0 0 tr tr tr tr v s. tr

TABLE 6 Example Number 13 14 15 16 17 % Al₂TiO₅ 80 80 80 80 80 % Mullite 20 20 20 20 20 Weight Percent MoO₃ 2.00 2.00 — 2.00 — Y₂O₃ 2.00 2.00 2.00 2.00 2.00 Alumina C 41.48 41.48 41.48 36.18 36.18 Aluminum hydroxide C 20.00 20.00 20.00 20.00 20.00 Titania A 33.27 33.27 33.27 32.73 32.73 Kaolin A — — — 11.09 11.09 Quartz B 5.25 5.25 5.25 — — Graphite A 25.00 — — — — Graphite B — 25.00 25.00 25.00 25.00 MPS Alumina sources 12.9 12.9 12.9 13.3 13.3 MPS Titania source 0.50 0.50 0.50 0.50 0.50 MPS Quartz 23.4 23.4 23.4 — — MPS All Inorganic 9.3 9.3 9.3 8.7 8.7 Raw Materials Firing and Properties Firing Temperature 1400 1400 1400 1400 1400 (° C.) Hold Time (hours) 4 4 4 4 4 CTE (RT-1000° C.) 6.6 0.5 8.3 1.7 4.8 % Porosity 49.2 52.1 49.5 53.4 51.2 d₅₀ 10.1 11.1 10.5 8.6 8.6 d₁₀ 6.3 6.7 6.0 4.9 4.6 d₉₀ 14.2 13.1 23.4 17.7 19.7 (d₅₀ − d₁₀)/d₅₀ 0.37 0.40 0.42 0.43 0.46 (d₉₀ − d₁₀)/d₅₀ 0.79 0.58 1.65 1.48 1.76 MOR rod (psi) 710 721 793 604 768 Al₂TiO₅ M M M M M Mullite m m m m m Al₂O₃ tr tr tr tr tr TiO₂ tr tr tr tr tr

TABLE 7 Example Number 18 19 20 21 22 % Al₂TiO₅ 70 70 70 70 70 % Mullite 30 30 30 30 30 Weight Percent MoO₃ 2.00 2.00 — 2.00 — Y₂O₃ 2.00 2.00 2.00 2.00 2.00 Alumina C 43.01 43.01 43.01 35.10 35.10 Aluminum hydroxide C 20.00 20.00 20.00 20.00 20.00 Titania A 29.12 29.12 29.12 28.40 28.40 Kaolin A — — — 16.50 16.50 Quartz B 7.87 7.87 7.87 — — Graphite A 25.00 — — — — Graphite B — 25.00 25.00 25.00 25.00 MPS Alumina sources 12.8 12.8 12.8 13.4 13.4 MPS Titania source 0.50 0.50 0.50 0.50 0.50 MPS Quartz 23.4 23.4 23.4 — — MPS All Inorganic 10.1 10.1 10.1 9.1 9.1 Raw Materials Firing and Properties Firing Temperature 1400 1400 1400 1400 1400 (° C.) Hold Time (hours) 4 4 4 4 4 CTE (RT-1000° C.) 8.9 8.6 8.4 14.0 14.1 % Porosity 51.5 53.9 52.7 53.8 54.0 d₅₀ 10.3 11.1 11.3 8.1 8.1 d₁₀ 6.1 5.9 5.8 4.4 4.0 d₉₀ 15.3 21.2 22.9 14.9 18.8 (d₅₀ − d₁₀)/d₅₀ 0.41 0.47 0.48 0.46 0.50 (d₉₀ − d₁₀)/d₅₀ 0.89 1.39 1.52 1.30 1.81 MOR rod (psi) 876 663 1091 726 765 Al₂TiO₅ M M M M M Mullite m m m m m Al₂O₃ tr tr tr v.s.tr s.tr TiO₂ tr tr tr v.s.tr s.tr

TABLE 8 Example Number 23 24 25 26 27 % Al₂TiO₅ 80 80 80 80 80 % Mullite 20 20 20 20 20 Weight Percent MoO₃ 2.00 2.00 — 2.00 — Y₂O₃ 2.00 2.00 2.00 2.00 2.00 Alumina C 41.48 41.48 41.48 36.18 36.18 Aluminum hydroxide C 20.00 20.00 20.00 20.00 20.00 Titania A 33.27 33.27 33.27 32.73 32.73 Kaolin A — — — 11.09 11.09 Quartz B 5.25 5.25 5.25 — — Graphite A 25.00 — — — — Graphite B — 25.00 25.00 25.00 25.00 MPS Alumina sources 12.9 12.9 12.9 13.3 13.3 MPS Titania source 0.50 0.50 0.50 0.50 0.50 MPS Quartz 23.4 23.4 23.4 — — MPS All Inorganic 9.3 9.3 9.3 8.7 8.7 Raw Materials Firing and Properties Firing Temperature 1500 1500 1500 1500 1500 (° C.) Hold Time (hours) 4 4 4 4 4 CTE (RT-1000° C.) −2.0 −8.4 0.1 −4.5 −2.2 % Porosity 47.6 50.2 47.0 50.7 47.3 d₅₀ 11.2 11.6 11.6 10.0 10.0 d₁₀ 8.2 — 7.6 6.5 6.8 d₉₀ 37.3 — 20.8 19.4 19.2 (d₅₀ − d₁₀)/d₅₀ 0.27 — 0.34 0.35 0.32 (d₉₀ − d₁₀)/d₅₀ 2.60 — 1.14 1.29 1.24 MOR rod (psi) 593 489 706 489 670 Al₂TiO₅ M M M M M Mullite m m m m m Al₂O₃ v.s.tr v.s.tr s.tr s.tr tr TiO₂ v.s.tr v.s.tr s.tr v.s.tr v.s.tr

TABLE 9 Example Number 28 29 30 31 32 % Al₂TiO₅ 70 70 70 70 70 % Mullite 30 30 30 30 30 Weight Percent MoO₃ 2.00 2.00 — 2.00 — Y₂O₃ 2.00 2.00 2.00 2.00 2.00 Alumina C 43.01 43.01 43.01 35.10 35.10 Aluminum hydroxide C 20.00 20.00 20.00 20.00 20.00 Titania A 29.12 29.12 29.12 28.40 28.40 Kaolin A — — — 16.50 16.50 Quartz B 7.87 7.87 7.87 — — Graphite A 25.00 — — — — Graphite B — 25.00 25.00 25.00 25.00 MPS Alumina sources 12.8 12.8 12.8 13.4 13.4 MPS Titania source 0.50 0.50 0.50 0.50 0.50 MPS Quartz 23.4 23.4 23.4 — — MPS All Inorganic 10.1 10.1 10.1 9.1 9.1 Raw Materials Firing and Properties Firing Temperature 1500 1500 1500 1500 1500 (° C.) Hold Time (hours) 4 4 4 4 4 CTE (RT-1000° C.) 2.9 0.6 0.7 3.3 2.8 % Porosity 49.2 53.7 50.0 49.3 49.8 d₅₀ 11.0 12.6 12.4 9.1 9.4 d₁₀ 7.5 8.1 7.8 5.5 5.7 d₉₀ 16.2 20.1 27.0 25.2 19.8 (d₅₀ − d₁₀)/d₅₀ 0.32 0.36 0.37 0.39 0.40 (d₉₀ − d₁₀)/d₅₀ 0.79 0.96 1.55 2.16 1.51 MOR rod (psi) 694 630 780 753 728 Al₂TiO₅ M M M M M Mullite m m m m m Al₂O₃ s.tr v.s.tr v.s.tr v.s.tr v.s.tr TiO₂ v.s.tr v.s.tr v.s.tr 0 v.s.tr

TABLE 10 Example Number 33 34 35 C11 C12 C13 % Al₂TiO₅ 80 80 80 80 80 80 % Mullite 20 20 20 20 20 20 Weight Percent Y₂O₃ 5.00 2.00 1.00 0.50 0.20 0.10 Alumina C 41.48 41.48 41.48 41.48 41.48 41.48 Aluminum 20.00 20.00 20.00 20.00 20.00 20.00 hydroxide C Titania A 33.27 33.27 33.27 33.27 33.27 33.27 Quartz B 5.25 5.25 5.25 5.25 5.25 5.25 Graphite A 25.00 25.00 25.00 25.00 25.00 25.00 MPS Alumina 12.9 12.9 12.9 12.9 12.9 12.9 sources MPS Titania 0.50 0.50 0.50 0.50 0.50 0.50 source MPS Quartz 23.4 23.4 23.4 23.4 23.4 23.4 MPS All 9.3 9.3 9.3 9.3 9.3 9.3 Inorganic Raw Materials Firing and Properties Firing 1400 1400 1400 1400 1400 1400 Temperature (° C.) Hold Time 4 4 4 4 4 4 (hours) CTE 6.0 5.7 9.2 14.9 21.9 35.5 (RT-1000° C.) % Porosity 44.7 48.0 52.2 51.4 47.6 49.3 d₅₀ 9.9 9.2 8.8 7.2 6.0 5.8 d₁₀ — — — — — — d₉₀ — — — — — — (d₅₀ − d₁₀)/d₅₀ — — — — — — (d₉₀ − d₁₀)/d₅₀ — — — — — — MOR rod (psi) 1213 1174 1450 916 1003 1048 Al₂TiO₅ — — — — — — Mullite — — — — — — Al₂O₃ — — — — — — TiO₂ — — — — — —

TABLE 11 Example Number C14 36 37 38 39 C15 % Al₂TiO₅ 80 80 80 80 80 80 % Mullite 20 20 20 20 20 20 Weight Percent Y₂O₃ 5.00 2.00 1.00 0.50 0.20 0.10 Alumina C 41.48 41.48 41.48 41.48 41.48 41.48 Aluminum 20.00 20.00 20.00 20.00 20.00 20.00 hydroxide C Titania A 33.27 33.27 33.27 33.27 33.27 33.27 Quartz B 5.25 5.25 5.25 5.25 5.25 5.25 Graphite A 25.00 25.00 25.00 25.00 25.00 25.00 MPS Alumina 12.9 12.9 12.9 12.9 12.9 12.9 sources MPS Titania 0.50 0.50 0.50 0.50 0.50 0.50 source MPS Quartz 23.4 23.4 23.4 23.4 23.4 23.4 MPS All 9.3 9.3 9.3 9.3 9.3 9.3 Inorganic Raw Materials Firing and Properties Firing 1500 1500 1500 1500 1500 1500 Temperature (° C.) Hold Time 4 4 4 4 4 4 (hours) CTE −0.9 −2.8 −2.1 3.8 6.5 10.7 (RT-1000° C.) % Porosity 36.8 47.2 49.9 51.2 52.6 55.2 d₅₀ 13.5 10.6 10.1 9.1 8.0 7.7 d₁₀ — — — — — — d₉₀ — — — — — — (d₅₀ − d₁₀)/d₅₀ — — — — — — (d₉₀ − d₁₀)/d₅₀ — — — — — — MOR rod (psi) 942 751 819 808 831 909 Al₂TiO₅ — — — — — — Mullite — — — — — — Al₂O₃ — — — — — — TiO₂ — — — — — —

TABLE 12 Example Number 40 41 42 43 44 45 46 47 48 % Al₂TiO₅ 70 70 70 70 70 70 70 70 70 % Mullite 30 30 30 30 30 30 30 30 30 Weight Percent Y₂O₃ 2.63 — — — — — — — — CeO₂ — 3.84 — — — — — — — La₂O₃ — — 3.42 — — — — — — Nd₂O₃ — — — 3.81 — — — — — Pr₆O₁₁ — — — — 3.63 — — — — Sm₂O₃ — — — — — 3.89 — — — Gd₂O₃ — — — — — — 3.90 — — Dy₂O₃ — — — — — — — 4.10 — Calcined Bastnasite — — — — — — — — 4.90 Alumina C 43.01 43.01 43.01 43.01 43.01 43.01 43.01 43.01 43.01 Aluminum hydroxide C 20.00 20.00 20.00 20.00 20.00 20.00 20.00 20.00 20.00 Titania A 29.12 29.12 29.12 29.12 29.12 29.12 29.12 29.12 29.12 Quartz C 7.87 7.87 7.87 7.87 7.87 7.87 7.87 7.87 7.87 Graphite A 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 12.8 12.8 12.8 12.8 12.8 12.8 12.8 12.8 12.8 MPS Titania source 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 MPS Quartz 25.4 25.4 25.4 25.4 25.4 25.4 25.4 25.4 25.4 MPS Inorganic Raw 10.2 10.2 10.2 10.2 10.2 10.2 10.2 10.2 10.2 Materials Firing and Properties Firing Temperature (° C.) 1400 1400 1400 1400 1400 1400 1400 1400 1400 Hold Time (hours) 4 4 4 4 4 4 4 4 4 CTE (RT-1000° C.) 5.7 8.2 11.9 6.1 6.4 8.9 11.0 7.4 11.4 % Porosity 47.7 39.6 42.1 39.9 40.5 43.2 44.4 48.4 45.1 d₅₀ 9.9 11.8 9.3 10.5 10.2 11.0 9.8 10.4 11.6 d₁₀ — — — — — — — — — d₉₀ — — — — — — — — — (d₅₀ − d₁₀)/d₅₀ — — — — — — — — — (d₉₀ − d₁₀)/d₅₀ — — — — — — — — — MOR rod (psi) 1055 1362 1504 1299 1193 1270 1155 1015 1355 Al₂TiO₅ — — — — — — — — — Mullite — — — — — — — — — Al₂O₃ — — — — — — — — — TiO₂ — — — — — — — — —

TABLE 13 Example Number 49 50 51 52 53 54 55 56 57 % Al₂TiO₅ 70 70 70 70 70 70 70 70 70 % Mullite 30 30 30 30 30 30 30 30 30 Weight Percent Y₂O₃ 2.63 — — — — — — — — CeO₂ — 3.84 — — — — — — — La₂O₃ — — 3.42 — — — — — — Nd₂O₃ — — — 3.81 — — — — — Pr₆O₁₁ — — — — 3.63 — — — — Sm₂O₃ — — — — — 3.89 — — — Gd₂O₃ — — — — — — 3.90 — — Dy₂O₃ — — — — — — — 4.10 — Calcined Bastnasite — — — — — — — — 4.90 Alumina C 43.01 43.01 43.01 43.01 43.01 43.01 43.01 43.01 43.01 Aluminum hydroxide C 20.00 20.00 20.00 20.00 20.00 20.00 20.00 20.00 20.00 Titania A 29.12 29.12 29.12 29.12 29.12 29.12 29.12 29.12 29.12 Quartz C 7.87 7.87 7.87 7.87 7.87 7.87 7.87 7.87 7.87 Graphite A 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 12.8 12.8 12.8 12.8 12.8 12.8 12.8 12.8 12.8 MPS Titania source 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 MPS Quartz 25.4 25.4 25.4 25.4 25.4 25.4 25.4 25.4 25.4 MPS Inorganic Raw 10.2 10.2 10.2 10.2 10.2 10.2 10.2 10.2 10.2 Materials Firing and Properties Firing Temperature (° C.) 1500 1500 1500 1500 1500 1500 1500 1500 1500 Hold Time (hours) 4 4 4 4 4 4 4 4 4 CTE (RT-1000° C.) −0.9 1.0 4.6 3.5 2.7 1.5 1.0 0.0 4.3 % Porosity 43.7 41.4 42.9 40.2 38.7 42.4 44.0 44.9 44.2 d₅₀ 12.0 13.2 10.8 12.2 12.3 12.9 11.9 12.3 13.7 d₁₀ — — — — — — — — — d₉₀ — — — — — — — — — (d₅₀ − d₁₀)/d₅₀ — — — — — — — — — (d₉₀ − d₁₀)/d₅₀ — — — — — — — — — MOR rod (psi) 931 1106 1188 1218 1208 1095 1011 940 1011 Al₂TiO₅ — — — — — — — — — Mullite — — — — — — — — — Al₂O₃ — — — — — — — — — TiO₂ — — — — — — — — —

TABLE 14 Example Number 58 59 C16 C17 C18 % Al₂TiO₅ 80 80 80 80 80 % Mullite 20 20 20 20 20 Weight Percent Y₂O₃ 2.78 — — — — CaCO₃ — 1.88 — — SrCO₃ — — 2.61 — — In₂O₃ — — — 3.88 — SnO₂ — — — — 3.86 Alumina C 41.48 41.48 41.48 41.48 41.48 Aluminum hydroxide C 20.00 20.00 20.00 20.00 20.00 Titania A 33.27 33.27 33.27 33.27 33.27 Quartz B 5.25 5.25 5.25 5.25 5.25 Quartz C — — — — — Graphite A 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 12.9 12.9 12.9 12.9 12.9 MPS Titania source 0.50 0.50 0.50 0.50 0.50 MPS Quartz 23.4 23.4 23.4 23.4 23.4 MPS All Inorganic 9.3 9.3 9.3 9.3 9.3 Raw Materials Firing and Properties Firing Temperature 1400 1400 1400 1400 1400 (° C.) Hold Time (hours) 4 4 4 4 4 CTE (RT-1000° C.) 5.3 14.0 30.0 45.3 63.4 % Porosity 47.7 49.8 48.7 52.7 48.1 d₅₀ 9.4 10.4 7.6 6.1 4.2 d₁₀ — — — — — d₉₀ — — — — — (d₅₀ − d₁₀)/d₅₀ — — — — — (d₉₀ − d₁₀)/d₅₀ — — — — — MOR rod (psi) 904 1207 1266 877 1778 Al₂TiO₅ M M M M M Mullite m 0 0 m m Al₂O₃ tr m m m M TiO₂ tr m m M M

TABLE 15 Example Number 60 61 C19 C20 C21 % Al₂TiO₅ 80 80 80 80 80 % Mullite 20 20 20 20 20 Weight Percent Y₂O₃ 2.78 — — — — CaCO₃ — 1.88 — — — SrCO₃ — — 2.61 — — In₂O₃ — — — 3.88 — SnO₂ — — — 3.86 Alumina C 41.48 41.48 41.48 41.48 41.48 Aluminum hydroxide C 20.00 20.00 20.00 20.00 20.00 Titania A 33.27 33.27 33.27 33.27 33.27 Quartz B 5.25 5.25 5.25 5.25 5.25 Graphite A 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 12.9 12.9 12.9 12.9 12.9 MPS Titania source 0.50 0.50 0.50 0.50 0.50 MPS Quartz 23.4 23.4 23.4 23.4 23.4 MPS All Inorganic 9.3 9.3 9.3 9.3 9.3 Raw Materials Firing and Properties Firing Temperature 1500 1500 1500 1500 1500 (° C.) Hold Time (hours) 4 4 4 4 4 CTE (RT-1000° C.) −1.6 11.3 16.9 12.1 28.6 % Porosity 44.9 44.0 49.5 53.7 54.8 d₅₀ 11.4 10.4 10.5 11.6 6.9 d₁₀ — — — — — d₉₀ — — — — — (d₅₀ − d₁₀)/d₅₀ — — — — — (d₉₀ − d₁₀)/d₅₀ — — — — — MOR rod (psi) 823 873 828 480 765 Al₂TiO₅ M M M M M Mullite m tr 0 m m Al₂O₃ tr m m v.s.tr tr TiO₂ v.s.tr tr m tr tr

TABLE 16 Example Number C22 C23 C24 C25 C26 C27 C28 % Al₂TiO₅ 80 80 80 80 80 80 80 % Mullite 20 20 20 20 20 20 20 Weight Percent Bi₂O₃ 4.75 — — — — — — MoO₃ — 2.61 — — — — — B₂O₃ — — 1.37 — — — — Nb₂O₅ — — — 2.48 — — — WO₃ — — — — 3.98 — — ZnO — — — — — 3.11 — ZrO₂ — — — — — — 3.11 Alumina A 53.52 53.52 53.52 53.52 53.52 53.52 53.52 Titania A 34.56 34.56 34.56 34.56 34.56 34.56 34.56 Kaolin A 11.92 11.92 11.92 11.92 11.92 11.92 11.92 Graphite A 25.00 25.00 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 6.8 6.8 6.8 6.8 6.8 6.8 6.8 MPS Titania source 0.50 0.50 0.50 0.50 0.50 0.50 0.50 MPS Quartz — — — — — — — MPS All Inorganic Raw Materials 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Firing and Properties Firing Temperature (° C.) 1400 1400 1400 1400 1400 1400 1400 Hold Time (hours) 4 4 4 4 4 4 4 CTE (RT-1000° C.) 37.1 26.4 36.5 41.4 50.6 36.5 43.7 % Porosity 49.1 52.3 51.8 51.0 53.8 47.9 50.2 d₅₀ 5.2 4.5 4.1 2.8 2.8 3.7 3.0 d₁₀ — — — — — — — d₉₀ — — — — — — — (d₅₀ − d₁₀)/d₅₀ — — — — — — — (d₅₀ − d₁₀)/d₅₀ — — — — — — — MOR rod (psi) 1416 1164 1599 2165 1817 1827 2094 Al₂TiO₅ M M M M M M M Mullite m m m m m m m Al₂O₃ m tr tr M M 0 tr TiO₂ m tr m M M tr 0

TABLE 17 Example Number C29 C30 C31 C32 C33 C34 C35 % Al₂TiO₅ 80 80 80 80 80 80 80 % Mullite 20 20 20 20 20 20 20 Weight Percent Bi₂O₃ 4.75 — — — — — — MoO₃ — 2.61 — — — — — B₂O₃ — — 1.37 — — — — Nb₂O₅ — — — 2.48 — — — WO₃ — — — — 3.98 — — ZnO — — — — — 3.11 — ZrO₂ — — — — — — 3.11 Alumina A 53.52 53.52 53.52 53.52 53.52 53.52 53.52 Titania A 34.56 34.56 34.56 34.56 34.56 34.56 34.56 Kaolin A 11.92 11.92 11.92 11.92 11.92 11.92 11.92 Graphite A 25.00 25.00 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 6.8 6.8 6.8 6.8 6.8 6.8 6.8 MPS Titania source 0.50 0.50 0.50 0.50 0.50 0.50 0.50 MPS Quartz — — — — — — — MPS All Inorganic Raw Materials 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Firing and Properties Firing Temperature (° C.) 1500 1500 1500 1500 1500 1500 1500 Hold Time (hours) 4 4 4 4 4 4 4 CTE (RT-1000° C.) 9.0 16.5 30.3 26.2 24.8 24.7 20.0 % Porosity 41.9 55.1 51.8 48.6 51.4 46.7 50.7 d₅₀ 5.1 4.0 4.1 5.0 5.2 4.3 4.9 d₁₀ — — — — — — — d₉₀ — — — — — — — (d₅₀ − d₁₀)/d₅₀ — — — — — — — (d₉₀ − d₁₀)/d₅₀ — — — — — — — MOR rod (psi) 966 881 1120 1131 959 1343 1027 Al₂TiO₅ M M M M M M M Mullite m m m m m m m Al₂O₃ tr tr v.s.tr 0 tr 0 0 TiO₂ tr tr v.s.tr tr m 0 0

TABLE 18 Example Number 63 64 65 66 67 68 69 70 % Al₂TiO₅ 70 70 70 70 70 70 70 70 % Mullite 30 30 30 30 30 30 30 30 Weight Percent Y₂O₃ 2.63 2.63 2.63 2.63 2.63 2.63 2.63 2.63 Alumina A — — — — — — — — Alumina B 43.01 — — — 43.01 — — — Alumina C — 43.01 — — — 43.01 — — Alumina D — — 43.01 — — — 43.01 — Alumina E — — — 43.01 — — — 43.01 Aluminum hydroxide C 20.00 20.00 20.00 20.00 20.00 20.00 20.00 20.00 Titania A 29.12 29.12 29.12 29.12 29.12 29.12 29.12 29.12 Quartz C 7.87 7.87 7.87 7.87 7.87 7.87 7.87 7.87 Graphite A 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 12.8 12.8 22.9 35.2 12.8 12.8 22.9 35.2 MPS Titania source 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 MPS Quartz 25.4 25.4 25.4 25.4 25.4 25.4 25.4 25.4 MPS Inorganic Raw Materials 10.2 10.2 16.6 24.3 10.2 10.2 16.6 24.3 Firing and Properties Firing Temperature (° C.) 1400 1400 1400 1400 1500 1500 1500 1500 Hold Time (hours) 4 4 4 4 4 4 4 4 CTE (RT-1000° C.) 10.4 9.8 7.5 6.1 1.4 2.8 −0.7 −3.8 % Porosity 44.7 50.3 48.2 50.0 41.6 45.2 47.8 48.4 d₅₀ 8.7 10.0 13.7 17.6 9.8 11.4 15.1 21.4 d₁₀ 5.8 6.5 9.5 12.8 7.3 8.3 10.6 15.0 d₉₀ 12.4 15.5 20.1 26.5 13.7 20.2 26.9 31.2 (d₅₀ − d₁₀)/d₅₀ 0.33 0.35 0.31 0.27 0.25 0.27 0.30 0.30 (d₉₀ − d₁₀)/d₅₀ 0.76 0.90 0.78 0.78 0.65 1.05 1.08 0.75 MOR rod (psi) 1439 1174 959 710 1175 1017 753 505 Al₂TiO₅ — — — — — — — — Mullite — — — — — — — — Al₂O₃ — — — — — — — — TiO₂ — — — — — — — —

TABLE 19 Example Number 71 72 73 74 75 % Al₂TiO₅ 70 70 70 70 70 % Mullite 30 30 30 30 30 Weight Percent Y₂O₃ 2.50 2.50 2.63 2.63 2.50 Alumina C — — 43.01 43.01 43.01 Alumina E 43.01 43.01 — — — Aluminum hydroxide C 20.00 20.00 20.00 20.00 20.00 Titania A 29.12 29.12 — — — Titania B — — 29.12 29.12 — Titania C — — — — 31.83 Quartz C 7.87 7.87 7.87 7.87 7.87 Graphite A 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 35.2 35.2 12.8 12.8 12.8 MPS Titania source 0.50 0.50 13.69 13.69 22.68 MPS Quartz 25.4 25.4 25.4 25.4 25.4 MPS All Inorganic Raw Materials 24.3 24.3 14.1 14.1 16.8 Firing and Properties Firing Temperature (° C.) 1450 1450 1400 1500 1450 Hold Time (hours) 6 8 4 4 6 CTE (RT-1000° C.) 0.8 −2.7 12.5 5.1 6.3 % Porosity 48.4 49.0 56.9 53.9 58.0 d₅₀ 18.1 18.8 13.3 15.5 12.4 d₁₀ 12.2 12.7 9.8 11.8 10.2 d₉₀ 26.4 30.8 17.6 19.7 22.3 (d₅₀ − d₁₀)/d₅₀ 0.33 0.32 0.26 0.24 0.18 (d₉₀ − d₁₀)/d₅₀ 0.78 0.97 0.59 0.51 0.97 MOR rod (psi) — — 646 520 — Diameter (cm) — 14.46 — — — Height (cm) — 15.29 — — — Cells per square inch — 311 — — — Wall Thickness (10⁻³ in) — 11.2 — — — Mass (g) — 1713 — — — Approx. Filter Bulk Density (g/cm³) — 0.681 — — — Pressure drop at 0 g/L, 210 scfm (kPa) — 1.54 — — — Pressure drop at 5 g/L, 210 scfm (kPa) — 3.87 — — —

TABLE 20 Example Number 76 77 78 79 80 81 % Al₂TiO₅ 80 80 80 80 80 80 % Mullite 20 20 20 20 20 20 Weight Percent MoO₃ 2.00 2.00 2.00 2.00 2.00 2.00 Y₂O₃ 2.00 2.00 2.00 2.00 2.00 2.00 Alumina C 41.48 41.48 41.48 41.48 41.48 41.48 Aluminum hydroxide A 20.00 20.00 20.00 20.00 20.00 20.00 Titania A 33.27 33.27 33.27 33.27 33.27 33.27 Quartz A 5.25 5.25 5.25 5.25 5.25 5.25 Graphite A 25.00 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 9.8 9.8 9.8 9.8 9.8 9.8 MPS Titania source 0.5 0.5 0.5 0.5 0.5 0.5 MPS Quartz 3.7 3.7 3.7 3.7 3.7 3.7 MPS All Inorganic Raw Materials 6.4 6.4 6.4 6.4 6.4 6.4 Firing and Properties Firing Temperature (° C.) 1415 1435 1435 1435 1455 1475 Hold Time (hours) 8 6 6 6 6 6 Kiln Type (E = electric, G = gas) E G E G G E CTE (RT-1000° C.) −2.3 −3.6 −4.1 1.1 −0.2 −6.1 % Porosity 50.5 48.7 49.3 51.1 50.0 47.7 d₅₀ 10.0 9.2 9.7 9.7 9.9 10.4 d₁₀ — — 6.4 — — — d₉₀ — — 13.7 — — — (d₅₀ − d₁₀)/d₅₀ — — 0.34 — — — (d₉₀ − d₁₀)/d₅₀ — — 0.76 — — — Diameter (cm) — — 4.95 — — — Height (cm) — — 15.24 — — — Cells per square inch — — 191 — — — Wall Thickness (10⁻³ in) — — 14.0 — — — Mass (g) — — 211.8 — — — Approx. Filter Bulk Density (g/cm³) — — 0.721 — — — Pressure drop at 0 g/L, 26.25 scfm (kPa) — — 1.87 — — — Pressure drop at 5 g/L, 26.25 scfm (kPa) — — 4.51 — — —

TABLE 21 Example Number 82 83 84 85 86 87 88 % Al₂TiO₅ 80 80 80 80 80 80 80 % Mullite 20 20 20 20 20 20 20 Weight Percent Y₂O₃ 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Alumina C 41.48 41.48 41.48 41.48 41.48 41.48 41.48 Aluminum hydroxide A 20.00 20.00 20.00 20.00 20.00 20.00 20.00 Titania A 33.27 33.27 33.27 33.27 33.27 33.27 33.27 Quartz A 5.25 5.25 5.25 5.25 5.25 5.25 5.25 Graphite A 25.00 25.00 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 9.8 9.8 9.8 9.8 9.8 9.8 9.8 MPS Titania source 0.5 0.5 0.5 0.5 0.5 0.5 0.5 MPS Quartz 3.7 3.7 3.7 3.7 3.7 3.7 3.7 MPS All Inorganic Raw Materials 6.4 6.4 6.4 6.4 6.4 6.4 6.4 Firing and Properties Firing Temperature (° C.) 1415 1435 1455 1465 1475 1475 1435 Hold Time (hours) 8 6 6 4 6 6 6 Kiln Type (E = electric, G = gas) E G G E E G E CTE (RT-1000° C.) −0.5 −3.5 0.7 −5.1 −4.3 −0.3 — % Porosity 48.3 48.7 48.5 46.5 46.9 49.9 — d₅₀ 9.7 9.5 10.5 10.2 10.5 10.7 — d₁₀ — — — — — — — d₉₀ — — — — — — — (d₅₀ − d₁₀)/d₅₀ — — — — — — — (d₉₀ − d₁₀)/d₅₀ — — — — — — — Diameter (cm) — — — 4.83 — — 4.89 Height (cm) — — — 15.30 — — 15.24 Cells per square inch — — — 208 — — 203 Wall Thickness (10⁻³ in) — — — 13.6 — — 12.7 Mass (g) — — — 214.9 — — 207.2 Approx. Filter Bulk Density (g/cm³) — — — 0.767 — — 0.724 Pressure drop at 0 g/L, 26.25 scfm — — — 2.02 — — 1.94 (kPa) Pressure drop at 5 g/L, 26.25 scfm — — — 5.48 — — 4.86 (kPa)

TABLE 22 Example Number 89 90 91 92 93 % Al₂TiO₅ 70 70 70 70 70 % Mullite 30 30 30 30 30 Weight Percent Y₂O₃ 2.00 2.00 2.00 2.00 2.00 Alumina C 43.01 43.01 43.01 43.01 43.01 Aluminum hydroxide C 20.00 20.00 20.00 20.00 20.00 Titania A 29.12 29.12 29.12 29.12 29.12 Quartz C 7.87 7.87 7.87 7.87 7.87 Graphite A 25.00 25.00 25.00 25.00 25.00 MPS Alumina sources 12.8 12.8 12.8 12.8 12.8 MPS Titania source 0.5 0.5 0.5 0.5 0.5 MPS Quartz 25.4 25.4 25.4 25.4 25.4 MPS All Inorganic Raw Materials 10.2 10.2 10.2 10.2 10.2 Firing and Properties Firing Temperature (° C.) 1415 1435 1435 1455 1475 Hold Time (hours) 8 6 6 6 6 Kiln Type (E = electric, G = gas) E G E G E CTE (RT-1000° C.) 6.5 4.1 5.1 3.9 3.6 % Porosity 47.8 51.8 49.3 50.5 48.4 d₅₀ 10.5 10.4 10.4 10.7 11.5 d₁₀ — — 6.9 — — d₉₀ — — 17.5 — — (d₅₀ − d₁₀)/d₅₀ — — 0.34 — — (d₉₀ − d₁₀)/d₅₀ — — 0.97 — — Diameter (cm) — — 4.91 4.96 — Height (cm) — — 15.24 15.34 — Cells per square inch — — 202 194 — Wall Thickness (10⁻³ in) — — 13.6 14.1 — Mass (g) — — 207.1 205.4 — Approx. Filter Bulk Density (g/cm³) — — 0.716 0.693 — Pressure drop at 0 g/L, 26.25 scfm (kPa) — — 1.89 1.73 — Pressure drop at 5 g/L, 26.25 scfm (kPa) — — 5.02 4.88 —

TABLE 23 Example Number 94 % Al₂TiO₅ 80 % Mullite 20 Weight Percent Y₂O₃ 2.00 Alumina B 41.48 Aluminum hydroxide C 20.00 Titania A 33.27 Quartz B 5.25 Graphite A 25 MPS Alumina sources 12.9 MPS Titania source 0.50 MPS Quartz 23.4 MPS All Inorganic Raw Materials 9.3 Firing and Properties Firing Temperature (° C.) 1425 Hold Time (hours) 10 % Porosity 48.8 d₅₀ 10.2 Pre- Post- Cycled Cycled % Length Change — +0.21% CTE (RT-1000° C.) on rod −2.2 −3.6 MOR rod (psi) 825 815 

1. A ceramic body comprising phase of mullite and aluminum titanate, and at least 0.10% by weight of a metal oxide for a metal selected from the group consisting of bismuth, calcium, yttrium, lanthanides and combinations thereof, while exhibiting a set of properties including a coefficient of thermal expansion (RT-1000° C.) less than 15×10⁻⁷ C⁻¹, a porosity of at least 38% by volume, a median pore diameter of at least 8 microns, and a narrow pore size distribution as characterized by the relation (d₅₀-d₁₀)/d₅₀ being less than 0.50 corresponding to a high degree of interconnected porosity.
 2. The ceramic body of claim 1 wherein the metal oxide is in an amount of between 0.10% to 5.0% by weight.
 3. The ceramic body of claim 2 wherein the metal is yttrium.
 4. The ceramic body of claim 1 wherein the ceramic body exhibits said set of properties when sintered to a temperature of between 1375° C. to 1550° C.
 5. A diesel exhaust particulate filter comprising the ceramic body of claim 1, wherein the ceramic body is a plugged, wall-flow honeycomb body having a plurality of parallel end-plugged cell channels traversing the body from a frontal inlet end to an outlet end thereof.
 6. The diesel exhaust particulate filter of claim 5 further exhibiting a coefficient of thermal expansion (RT-1000° C.) not greater than 10×10⁻⁷ C⁻¹, a porosity of between 45-60% by volume, a median pore diameter of between 10-20 microns, and a narrow pore size distribution as characterized by the relation (d₅₀-d₁₀)/d₅₀ being not greater than 0.35 corresponding to a high degree of interconnected porosity.
 7. A method for making a mullite-aluminum titanate ceramic body comprising: a. providing a mixture of inorganic raw materials comprising an alumina source, a silica source, and a titanium dioxide source, in combination with a source of a metal oxide as a sintering additive in an amount of at least 0.10% by weight super-addition, the source corresponding to an oxide of a metal selected from the group of metals consisting of bismuth, calcium, yttrium, lanthanides and combinations thereof, b. shaping the mixture into a body; and, c. sintering the body to a temperature of between 1375° C. to 1550° C. for a period of between 1 hour to 15 hours; wherein the weighted average of the median particle diameters of the inorganic raw materials, D₅₀, is at least 6 microns to form a pore size in the mullite-aluminum titanate ceramic body after sintering of at least 8 microns.
 8. The method of claim 7 wherein the metal oxide is added to the raw material mixture in an amount between 0.10% and 5.0% by weight.
 9. The method of claim 8 wherein the metal is yttrium.
 10. The method of claim 7 wherein an amount of at least 0.05% by weight of molybdenum oxide or tungsten oxide is further added to the mixture.
 11. The method of claim 7 wherein the alumina source is a selected from a group consisting of corundum, gamma-alumina or another transitional alumina, boehmite, alumina hydroxide (gibbsite) and mixtures thereof.
 12. The method of claim 11 wherein the alumina source has a median particle diameter greater than 15 microns.
 13. The method of claim 7 wherein the mixture of inorganic raw materials further includes an aluminosilicate source.
 14. The method of claim 13 wherein the aluminosilicate source is selected from the group consisting of mullite, kyanite, sillimanite, kaolin, calcined kaolin, pyrophyllite, and mixtures thereof.
 15. The method of claim 7 wherein the silica source is selected from the group consisting of quartz, cristobalite, zeolite, diatomaceous earth, fused silica, colloidal silica, amorphous silica, and combinations thereof.
 16. The method of claim 7 wherein the titanium dioxide source is selected from the group consisting of rutile, anatase, amorphous titania, and mixtures thereof.
 17. The method of claim 7 wherein the alumina source and titanium dioxide source have median particle or agglomerate diameters of at least 10 microns.
 18. The method of claim 7 wherein the metal oxide source is selected from the group consisting of bismuth oxide, calcium carbonate, calcium hydroxide, calcium aluminate, calcium titanate, calcium silicate, yttrium or rare earth oxide, hydroxide, carbonate, fluoride-carbonate, aluminate, silicate, titanate, chloride, nitrate, acetate, or other soluble or insoluble salt, a mixed rare earth concentrate such as bastnasite, calcined bastnasite, or monazite, and combinations thereof.
 19. The method of claim 18 wherein the metal oxide source has a median particle diameter of less than 5 microns.
 20. The method of claim 7 wherein the mixture is shaped by extrusion through a die to form a honeycomb structure. 